Radio communication device and radio communication method

ABSTRACT

Provided is a radio communication device capable of reducing interference, caused by non-SR transmission, with a basic service set (BSS) performing spatial reuse (SR) transmission. An SR transmission resource control unit ( 107 ) of the radio communication device (SR initiator) ( 100 ) determines transmission resources for an SR signal to be transmitted by means of SR to a second BSS other than a first BSS to which the radio communication device ( 100 ) belongs on the basis of radio quality information transmitted from other radio communication devices (SR responders) in the first BSS. A radio transmission/reception unit ( 101 ) transmits the SR signal by using the determined transmission resources.

TECHNICAL FIELD

The present disclosure relates to a radio communication apparatus and aradio communication method.

BACKGROUND ART

In Task Group ax of the Institute of Electrical and ElectronicsEngineers (IEEE) 802.11 working group, the technical specification ofIEEE 802.11ax (hereinafter, referred to as “11ax”) has been standardizedas the next standard of 802.11ac.

In the IEEE 802.11 standard, Basic Service Set (BSS) is defined as a setof terminals (sometimes called “station (STAs)”) that form a basic radionetwork. The BSS is formed of one access point (sometimes called “accesspoint (AP)” or “base station”) and a plurality of terminals in theinfrastructure mode and is formed of a plurality of terminals in the adhoc mode.

A BSS other than the BSS (intra-BSS) to which the terminal belongs iscalled “Overlapping BSS (OBSS) or inter-BSS.” In an environment where aplurality of BSSs exist adjacently, a radio wave interference from asurrounding OBSS increases, and the system performance degrades due to adecrease in transmission opportunities.

In this respect, in 11ax, in order to improve the system performance inan environment where BSSs exist densely, the introduction of spatialreuse (SR) which obtains a transmission opportunity by reusing the radioresource used by an OBSS has been specified (e.g., see Non-PatentLiterature (hereinafter, referred to as “NPL”) 1).

In NPL 1, two SRs called “OBSS Packet Detect (OBSS PD)-based SR” and“SRP based SR” are defined. In OBSS PD-based SR, STAs obtain atransmission opportunity by dynamically controlling a clear channelassessment (CCA) threshold based on the received power of a signalreceived from an OBSS (hereinafter, referred to as an “OBSS signal”) anda BSS-identifier (BSS color) of the OBSS. Further, in SRP based SR, STAsderive a transmission power that satisfies the condition that thetransmission power does not exceed the interference allowable value ofthe OBSS, based on the interference allowable value (“spatial reuseparameter (SRP)”) obtained from the OBSS signal and the received signalstrength (“received signal strength indication (RSSI”) of the OBSSsignal. The STA obtains a transmission opportunity by transmitting asignal with the derived transmission power while reducing theinterference given to the OBSS (e.g., see NPL 2).

Note that, in the following description, transmission to which the SR isapplied is referred to as “SR transmission,” and transmission to whichthe SR is not applied is referred to as “Non-SR transmission.” Further,in the following description, the signal to be transmitted by SRtransmission is referred to as “SR signal,” and the signal to betransmitted by Non-SR transmission is referred to as “Non-SR signal.”

CITATION LIST Non-Patent Literatures

-   NPL 1

IEEE 802.11-17/0075r8 “SRP-Based SR Operation”

-   NPL 2

IEEE 802.11-16/1476r21 “SRP based SR for HE Trigger-based PPDU”

-   NPL 3

IEEE 802.11-16/1216r2 “SR Field SRP Table for HE Trigger-Based PPDU”

SUMMARY

However, while the reduction of interference given to an OBSS by SRtransmission is taken into consideration, the reduction of interferencegiven to the BSS performing SR transmission by Non-SR transmission isnot sufficiently discussed.

One aspect of the present disclosure facilitates providing a radiocommunication apparatus and a radio communication method each enablingreduction of the interference given by Non-SR transmission to the BSSthat performs SR transmission.

A radio communication apparatus according to one aspect of the presentdisclosure includes: control circuitry, which, in operation, determinesa transmission resource for a Spatial Reuse (SR) signal based on radioquality information transmitted from another radio communicationapparatus in a first Basic Service Set (BSS), the SR signal beingtransmitted by SR for a second BSS which is a BSS other than the firstBSS; and transmission circuitry, which, in operation, transmits the SRsignal, using the transmission resource.

A radio communication method according to one aspect of the presentdisclosure includes: determining a transmission resource for a SpatialReuse (SR) signal based on radio quality information transmitted fromanother radio communication apparatus in a first Basic Service Set(BSS), the SR signal being transmitted by SR for a second BSS other thanthe first BSS; and transmitting the SR signal, using the transmissionresource.

Note that general or specific embodiments may be implemented as asystem, an apparatus, a method, an integrated circuit, a computerprogram or a recording medium, or any selective combination of thesystem, the apparatus, the method, the integrated circuit, the computerprogram, and the recording medium.

According to one aspect of the present disclosure, the interferencegiven by Non-SR transmission to the BSS that performs SR transmissioncan be reduced.

Additional benefits and advantages of the disclosed exemplaryembodiments will become apparent from the specification and drawings.The benefits and/or advantages may be individually obtained by variousembodiments and features of the specification and drawings, which neednot all be provided in order to obtain one or more of such benefitsand/or advantages.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating an operation example of SRP-based SR;

FIG. 2 is a diagram provided for describing a problem in SRP-based SR;

FIG. 3 is a block diagram illustrating a configuration example of a partof a radio communication apparatus according to Embodiment 1;

FIG. 4 is a block diagram illustrating a configuration example of a partof a radio communication apparatus (SR initiator) according toEmbodiment 1;

FIG. 5 is a block diagram illustrating a configuration example of a partof a radio communication apparatus (SR responder) according toEmbodiment 1;

FIG. 6 is a sequence diagram illustrating an operation example of asystem according to Embodiment 1;

FIG. 7 is a diagram illustrating an operation example of SRP-based SRaccording to Embodiment 1;

FIG. 8 is a diagram illustrating an operation example of SRP-based SRaccording to Embodiment 1;

FIG. 9 is a diagram illustrating an example of SR availabilityinformation in units of RUs, according to Embodiment 1;

FIG. 10 is a diagram illustrating an example of SR availabilityinformation in units of 20 MHz, according to Embodiment 1;

FIG. 11 is a diagram illustrating an example of SR availabilityinformation on SRG and Non-SRG, according to Embodiment 2;

FIG. 12 is a diagram illustrating an example of SR availabilityinformation in units of BSS colors, according to Embodiment 2;

FIG. 13 is a block diagram illustrating a configuration example of aradio communication apparatus (SR initiator) according to Embodiment 3;

FIG. 14 is a sequence diagram illustrating an operation example ofSRP-based SR using a preceding signal according to another embodiment;

FIG. 15 is a block diagram illustrating a configuration example of aradio communication apparatus (SR initiator) that performs SRP-based SR,using the preceding signal according to the other embodiment; and

FIG. 16 is a sequence diagram illustrating an operation example of OBSSPD-based SR, according to the other embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a detailed description will be given of embodiments of thepresent disclosure with reference to the accompanying drawings.

[SRP Based SR]

SRP based SR will be described in detail with reference to FIG. 1.

An AP (OBSS AP) that belongs to an OBSS existing around its BSStransmits a trigger frame which is a control signal promptingtransmission of an uplink signal (e.g., Orthogonal Frequency DivisionMultiple Access (OFDMA)) signal and which is addressed to the STA (OBSSSTA) in the OBSS to which the AP belongs. The data frame including thetrigger frame herein is called “Delayed SRP Physical layer Protocol DataUnit (DSRP PPDU).” The SR initiator of its BSS receives a DSRP PPDUtransmitted from the OBSS AP to the OBSS STA (see left side of FIG. 1).

Note that, “SR initiator” is an apparatus (AP or STA) that attempts SRtransmission when the SRP obtained by the received OBSS signal takes apredetermined value. Further, an apparatus (AP or STA) which is acommunication counterpart of the SR initiator in the SR transmission iscalled “SR responder.”

The SR initiator derives transmission power that reduces interference toan OBSS for the purpose of reusing the radio resource used by the OBSS.

Specifically, the SR initiator acquires a BSS color included inSIG-A-field of the received DSRP PPDU and the SRP of OBSS AP defined bya value of Spatial reuse subfield in Common field of the trigger frame(e.g., see NPL 3). The SRP is expressed by the following Equation 1.

SRP=TXPWR_(AP)+Acceptable receiver interference level_(AP)   (1)

In Equation 1, TXPWR_(AP) indicates the transmission power of an OBSSAP, and Acceptable receiver interference level_(AP) indicates theallowable interference level of the OBSS AP.

The SR initiator also measures an RSSI (RSSI_(Trigger frame)) of thereceived DSRP PPDU.

The SR initiator then derives the transmission power(TXPWR_(SR initiator)) for the SR signal from the following Equation 2,using an SRP and RSSI.

TXPWR_(SR initiator)<SRP−RSSI_(trigger frame)   (2)

The SR initiator transmits the SR signal to the SR responder, using thederived transmission power. Using the transmission power derived fromEquation 2 makes it possible to reduce the interference given to theOBSS by SR-transmission from the SR initiator to the SR responder (seeright side of FIG. 1).

In SRP-based SR, the SR initiator reuses the radio resource bytransmitting an SR signal with the derived transmission power to the SRresponder that belongs to the same BSS as the SR initiator during aperiod (SRP opportunity) in which an uplink signal of the OBSS STAdetected from the trigger frame is transmitted, thereby improving thesystem performance.

In a case where the SR initiator performs SR transmission to the SRresponder with the transmission power with reduced interference given toOBSS, herein, the SR signal is transmitted with a transmission powerlower than the normal transmission power. For this reason, it isdesirable that the interference in the SR responder be low.

However, as illustrated in FIG. 2, in a case where the SR responder isadjacent to the OBSS (STA1 in FIG. 2), the Non-SR transmission in theOBSS (STA1) becomes large interference to the SR responder, there arisesa concern that the reception success rate of the SR signal in the SRresponder is reduced. Further, the SR signal that has not beensuccessfully received in the SR responder possibly becomes aninterference source with respect to the OBSS which is closer to the SRinitiator than the OBSS subject to the interference reduction target(OBSS including the AP in FIG. 2), and which is not subject to theinterference reduction (OBSS including STA2 in FIG. 2).

Thus, depending on the radio channel state of the SR responder, therearises a case where the interference is given from the OBSS in the SRtransmission, and the reception success rate of the SR signal in SRresponder is reduced, resulting in degradation of the systemperformance.

Thus, in one aspect of the present disclosure, a method for reducing theinterference given from an OBSS in SR transmission will be described.

Embodiment 1 [Configuration of Radio Communication System]

In a radio communication system according to the present embodiment, aplurality of BSSs adjacently exist. In the radio communication system,at least one of the apparatuses (STAs or APs) that form a BSS performsSRP-based SR (i.e., reuse of radio resources used by OBSS) with respectto a surrounding OBSS.

Hereinafter, an SR initiator (radio communication apparatus) 100 and SRresponder (radio communication apparatus) 200 for performing SRP-basedSR are provided as examples. That is, radio communication apparatus 100transmits an SR signal to radio communication apparatus 200. Forexample, the SR initiator is an STA and the SR responder is an AP.

FIG. 3 is a block diagram illustrating a part of a configuration ofradio communication apparatus 100 (SR initiator) according to thepresent embodiment. In radio communication apparatus 100 illustrated inFIG. 3, SR transmission resource controller 107 determines atransmission resource for the SR signal transmitted by SR (e.g.,SRP-based SR) with respect to a second BSS (i.e., OBSS) other than afirst BSS, based on radio quality information transmitted from anotherradio communication apparatus (SR responder) in the first BSS. Radiotransceiver 101 transmits the SR signal, using the transmissionresource.

[Configuration of SR Initiator]

FIG. 4 is a block diagram illustrating a configuration example of radiocommunication apparatus 100 (SR initiator) according to the presentembodiment. Radio communication apparatus 100 determines a transmissionresource for the SR signal based on radio quality information from radiocommunication apparatus 200, which is the SR responder, and transmitsthe SR signal within a predetermined period.

Radio communication apparatus 100 includes radio transceiver 101,received power measurer 102, demodulator 103, decoder 104, SRtransmission power reducer 105, radio quality information holder 106, SRtransmission resource controller 107, encoder 108, preamble generator109, and modulator 110. Incidentally, SR transmission power reducer 105and SR transmission resource controller 107 form an SR controller.

Radio transceiver 101 receives a radio signal (OBSS signal) transmittedfrom an OBSS (e.g., OBSS AP or OBSS STA) via an antenna, appliespredetermined radio reception processing, such as down-conversion and/orA/D conversion to the radio signal, and outputs the received signalafter the radio reception processing to received power measurer 102 anddemodulator 103.

Further, radio transceiver 101 applies predetermined radio transmissionprocessing, such as D/A conversion and/or upconversion into a carrierfrequency, to a packet signal inputted from modulator 110, andtransmits, via the antenna, a high-frequency signal (i.e., SR signal)amplified according to the transmission power indicated by thetransmission power information (to be described, hereinafter) inputtedfrom SR transmission resource controller 107.

Received power measurer 102 measures the received power (e.g., RSSI),using the received signal (i.e., OBSS signal) inputted from radiotransceiver 101 and outputs the measured RSSI to SR transmission powerreducer 105.

Demodulator 103 detects a preamble included in the received signalinputted from radio transceiver 101, extracts the received dataincluding a trigger frame, based on the control information included inthe preamble, and demodulates the received data. Demodulator 103 outputsthe control information and the received data after the demodulation todecoder 104.

Decoder 104 decodes the received data based on the control informationincluded in the preamble inputted from demodulator 103 and acquires atrigger frame. Then, decoder 104 outputs the decoded trigger frame andthe control information included in the preamble to SR transmissionpower reducer 105 and SR transmission resource controller 107.

SR transmission power reducer 105 determines the presence or absence ofallowance for SR transmission based on the control information includedin the trigger frame inputted from decoder 104. For example, SRtransmission power reducer 105 determines that SR-transmission isallowed when the value of the spatial reuse subfield included in thecommon field of the trigger frame is other than “SRP_DISALLOW” and“SRP_AND_NON-SRG_OBSS-PD_PROHIBITED.” That is, SR transmission powerreducer 105 determines that SR transmission is not allowed (disallowed)when the value of spatial reuse subfield is “SRP_DISALLOW” or“SRP_AND_NON-SRG_OBSS-PD_PROHIBITED.”

When determining that the SR transmission is allowed, SR transmissionpower reducer 105 reduces the transmission power in SR transmission.Specifically, SR transmission power reducer 105 determines thetransmission power (TXPWR_(SR initiator)) satisfying Equation 2, usingthe SRP[dBm] included in the trigger frame and RSSI(RSSI_(trigger frame)) of the trigger frame inputted from received powermeasurer 102. SR transmission power reducer 105 outputs the informationindicating the determined transmission power to SR transmission resourcecontroller 107.

Meanwhile, when determining that the SR transmission is disallowed, SRtransmission power reducer 105 cancels the SR transmission by outputtingnothing to SR transmission resource controller 107 (output OFF) oroutputting information indicating that no SR transmission has beenperformed to SR transmission resource controller 107. Further, SRtransmission power reducer 105 may cancel SR transmission in a casewhere reduction to the transmission power satisfying Equation 2 isimpossible, for example, due to constraints on implementation and/or thelike.

Radio quality information holder 106 holds the radio quality informationreceived from radio communication apparatus 200 (SR responder). Forexample, radio quality information may be indicated from radiocommunication apparatus 200 via a management frame or a control frame ina predetermined cycle or at a predetermined timing. Further, the radioquality information may be information indicating radio quality for eachpredetermined band. For example, radio quality information holder 106outputs the most recently received radio quality information to SRtransmission resource controller 107. Note that, the radio qualityinformation will be described in detail, hereinafter.

SR transmission resource controller 107 determines the SR transmissionresource (e.g., time resource, frequency resource, transmission powerresource) for the SR signal to be transmitted in the SR transmission forthe OBSS. For example, SR transmission resource controller 107configures the time resource (also referred to as SRP opportunity) ofthe SR signal to be a time shorter than the trigger-based PPDU, based onthe information on the packet length of trigger-based PPDU (Non-SRsignal) acquired from the trigger frame. Further, SR transmissionresource controller 107 determines the availability of SR transmissionfor each band, based on radio quality information for each predeterminedband inputted from radio quality information holder 106 for thefrequency resource. Note that, SR transmission resource controller 107may cancel the SR transmission when there is no SR-sendable band.Further, SR transmission resource controller 107 also configures thetransmission power indicated in the information inputted from SRtransmission power reducer 105 for transmission power resource.

SR transmission resource controller 107 outputs the informationindicating the determined SR transmission resource (time resourceinformation, transmission band information, and/or transmission powerinformation) to each of encoder 108, preamble generator 109, and radiotransceiver 101.

Note that, a detailed description of a determination method for afrequency resource of an SR signal in SR transmission resourcecontroller 107 will be given, hereinafter.

Encoder 108 determines a PHY service data unit (PSDU) length that issendable in an interval indicated by the time resource informationinputted from SR transmission resource controller 107, encodes the SRsignal (including data and/or the like), using a modulation and codingscheme (MCS) obtained from a received quality estimation value (such asradio quality information) in radio communication apparatus 200 (SRresponder), and outputs the encoded signal to modulator 110.

Preamble generator 109 generates a preamble including controlinformation including band allocation information for the SR signal(also referred to as RU allocation information) and a reference signal,based on the transmission band information inputted from SR transmissionresource controller 107, and outputs the generated preamble to modulator110. Note that, a detailed description of a generation method for bandallocation information for SR signals will be given, hereinafter.

Modulator 110 applies modulation (e.g., quadrature amplitude modulation(QAM) modulation) to the signal inputted from encoder 108. Modulator 110then allocates the modulation signal to the band (SR-sendable band)indicated in the band allocation information for the SR signal includedin the preamble and applies Inverse Fast Fourier Transform (IFFT)processing to generate an orthogonal frequency division multiplexing(OFDM) signal, and generates a data signal composed of an OFDM signal.Then, modulator 110 generates a radio frame (packet signal) in which apreamble is added to the data signal, and outputs the packet signal toradio transceiver 101.

[Configuration of SR Responder]

FIG. 5 is a block diagram illustrating a configuration of radiocommunication apparatus 200 (SR responder) according to the presentembodiment. Radio communication apparatus 200 transmits the radioquality information (e.g., information on interference level, such asSignal to Interference and Noise Ratio (SINR)) for each predeterminedband to radio communication apparatus 100, which is an SR initiator, andreceives the SR signal from radio communication apparatus 100.

Radio communication apparatus 200 includes radio transceiver 201,demodulator 202, decoder 203, radio quality measurer 204, radio qualityinformation generator 205, and modulator 206.

Radio transceiver 201 receives a signal from a BSS (e.g., SR initiator)or an OBSS (e.g., OBSS AP or OBSS STA) via an antenna, appliespredetermined radio reception processing, such as down-conversion and/orA/D conversion to the received signal, and outputs the received signalafter the radio reception processing to demodulator 202 or radio qualitymeasurer 204.

Further, radio transceiver 201 applies predetermined radio transmissionprocessing, such as D/A conversion and/or up-conversion into the carrierfrequency to the signal (including radio quality information) inputtedfrom modulator 206, and broadcasts the radio quality information via theantenna to the STAs (including radio communication apparatus 100) in theBSS to which the apparatus belongs.

Demodulator 202 detects a preamble from the received signal inputtedfrom radio transceiver 201 and acquires the frequency allocationinformation from the band allocation information included in thepreamble. Then, demodulator 202 extracts the radio frame containing thedesired data (corresponding to the SR signal) based on the frequencyallocation information, and outputs the radio frame to decoder 203.

Decoder 203 decodes the received data (SR signal) based on the controlinformation included in the received signal inputted from demodulator202, and acquires the data included in the SR signal.

Radio quality measurer 204 measures the radio quality (received power orinterference level), using the received signal (e.g., an OBSS signal orthe signal of BSS to which the apparatus belongs) inputted from radiotransceiver 201 and outputs the measurement result to radio qualityinformation generator 205. Note that, a detailed description of theradio quality measurement in radio quality measurer 204 will be given,hereinafter.

Radio quality information generator 205 generates radio qualityinformation including the measurement result inputted from radio qualitymeasurer 204 and outputs the radio quality information to modulator 206.

Radio quality information generator 205, for example, generates amanagement frame or a control frame addressed to the SR initiator (radiocommunication apparatus 100) including the measurement result inputtedfrom radio quality measurer 204. When the SR responder is an AP, forexample, radio quality information generator 205 may use a beacon framewhich is a management frame, or a trigger frame which is a controlframe. Further, when the SR responder is an STA, radio qualityinformation generator 205 may use a bandwidth query report (BQR) as aresponse to the trigger frame that is transmitted by the AP (radiocommunication apparatus 100), which is the SR initiator, and whosetrigger type is bandwidth query report poll (BQRP).

Modulator 206 assigns the signal resulting from the application ofmodulation to the radio quality information inputted from radio qualityinformation generator 205 to a predetermined band, and outputs thesignal to radio transceiver 201.

[Operations of Radio Communication Apparatus 100 and Radio CommunicationApparatus 200]

Next, a detailed description will be given of operations of radiocommunication apparatus 100 and radio communication apparatus 200 of thepresent embodiment.

In the present embodiment, an SR initiator (radio communicationapparatus 100) determines an SR transmission resource (including atransmission band and transmission power) for the SR signal based on theradio quality information from the SR responder (radio communicationapparatus 200).

FIG. 6 is a sequence diagram illustrating an operation example of aradio communication system according to the present embodiment. FIG. 6illustrates an operation of a case where the SR initiator and SRresponder which belong to a predetermined BSS apply SRP-based SR to anOBSS (including OBSS AP and OBSS STA) adjacent to the BSS.

In FIG. 6, the SR responder (radio quality measurer 204) measures thereceived power level or interference level for each predetermined band,using a signal from a predetermined BSS or OBSS and generates radioquality information based on the measurement result (ST101). Then, theSR responder broadcasts the signal including the generated radio qualityinformation to the STAs (including the SR initiator) in the BSS (ST102).

Note that, in ST102, the radio quality information may be broadcasted ata predetermined timing or in a predetermined cycle defined in advance.For example, the SR responder may measure the radio quality in apredetermined cycle in ST101 and broadcast the radio quality informationeach time the radio quality is measured, or the radio qualityinformation may be broadcasted at a timing other than the timingsdescribed above.

The OBSS AP generates a trigger frame prompting an uplink transmissionto an OBSS STA and transmits the trigger frame addressed to the OBSS STA(ST103). The trigger frame transmitted from the OBSS AP to the OBSS STAis also received by the SR initiator.

The SR initiator (SR transmission power reducer 105) determines thetransmission power for the SR signal for reducing the interference tothe OBSS AP (hereinafter, may be referred to as SR transmission power),using the interference allowable value (SRP) of the OBSS AP acquiredfrom the trigger frame received from the OBSS AP in ST103, and the RSSImeasured using the trigger frame (ST104).

The SR initiator (SR transmission resource controller 107) determines anSR transmission period (SRP opportunity, i.e., time resource) based oninformation on the packet-length of the non-SR signal that istransmitted by the OBSS STA and that is acquired from the trigger framereceived from the OBSS AP in ST103 (ST105). Further, the SR initiator(SR transmission resource controller 107) determines a transmissionresource (frequency resource) for the SR signal with which a desiredreceived quality can be expected, based on the radio quality informationfor each predetermined band received from the SR responder in ST102(ST105).

Note that, in ST105, the SR initiator determines the transmissionresource for the SR signal when transmitting the SR signal in a Non-SRsignal transmission period (also called SRP opportunity) obtained basedon the trigger frame received in ST103, for example, and the SRinitiator may not determine a transmission resource for the SR signalwhen not transmitting the SR signal in the Non-SR signal transmissionperiod (e.g., when unsendable). This allows the SR initiator to performthe transmission resource control for the SR signal only whentransmission of an SR signal is required, so that it is possible toreduce the processing amount.

Meanwhile, the OBSS STA transmits an uplink signal (i.e., Non-SR signal)to the OBSS AP based on an indication by the trigger frame received fromthe OBSS AP in ST103 (ST106).

The SR initiator transmits the SR signal to the SR responder in the SRtransmission period (SRP opportunity) determined in ST105, using the SRtransmission power determined in ST104 and the transmission resourcedetermined in ST105 (ST107).

The SR responder receives the SR signal transmitted from the SRinitiator in ST107 and decodes the received SR signal (ST108).

Further, the OBSS AP also receives the Non-SR signal transmitted fromthe OBSS STA in ST106 and decodes the received Non-SR signal (ST109).

FIGS. 7 and 8 illustrate operation examples of SRP-based SR (SR resourcecontrol using radio quality information) according to the presentembodiment.

In FIG. 7, the SR responder broadcasts the radio quality informationindicating that the interference given from the OBSS is small to the SRinitiator. In this case, the SR initiator determines that the SRtransmission is available, based on the received radio qualityinformation. In this respect, the SR initiator performs an SRtransmission, using an available transmission resource (i.e., atransmission resource to which the interference given from the OBSS issmall and with which a desired received quality can be expected).

That is, in FIG. 7, the SR initiator transmits the SR signal, using aresource with the interference given due to a Non-SR signal from theOBSS STA is small, so that it is possible to reduce the occurrence of adecoding error of the SR signal in the SR responder.

Further, in FIG. 7, the SR signal transmitted from the SR initiatorpossibly becomes interference to the OBSS AP. However, the transmissionpower control (ST104 in FIG. 6) in the SR initiator reduces thetransmission power such that the interference power is equal to or lessthan the allowable value. This reduces the occurrence of decoding errorsof Non-SR signals in OBSS APs.

Further, in FIG. 7, an OBSS which is not subject to the interferencereduction processing for SR transmission (STA2 in FIG. 7) cannot performtransmission due to the interference given by the SR transmission.

Meanwhile, in FIG. 8, the SR responder broadcasts the radio qualityinformation indicating that the interference given from the OBSS islarge to SR initiators. In this case, the SR initiator determines thatSR transmission is not available, based on the received radio qualityinformation. Therefore, the SR initiator cancels the SR transmission.

That is, in FIG. 8, the SR initiator does not perform SR transmissionwith a resource where the interference due to the Non-SR signal from anOBSS STA is large and an decoding error of the SR signal in the SRresponder is likely to occur. Thus, since no SR signal transmitted inFIG. 8, it is possible to reduce the occurrence of decoding errors ofthe Non-SR signal in the OBSS AP. Furthermore, in FIG. 8, an OBSS whichis not subject to the interference reduction processing for SRtransmission (STA2 in FIG. 8) can perform transmission because there isno interference by SR transmission.

As illustrated in FIGS. 7 and 8, the SR initiator determines atransmission resource (bandwidth) with which an SR signal is sendable(hereinafter, may be referred to as “sendable transmission resource”)taking the interference due a Non-SR signal transmitted from an OBSS(OBSS STA, herein) into consideration, based on the radio qualityinformation from the SR responder, and transmits SR in a resource otherthan the sendable transmission resource. Accordingly, even when a Non-SRsignal possibly becomes the interference depending on a radio channelcondition (such as a surrounding environment) of the SR responder, theSR signal is transmitted in a band where the interference is small, andno SR signal is transmitted in a band where the interference is likelyto be received. Thus, the occurrence of decoding errors of SR signals inSR responders can be reduced.

[Determination Method for Frequency Resource for SR Signals]

Next, a detailed description will be given of a determination method fora frequency resource for SR signals in SR transmission resourcecontroller 107 of radio communication apparatus 100 (SR initiator).

SR transmission resource controller 107 determines the frequencyresource for an SR signal based on the radio quality informationreceived from radio communication apparatus 200 (SR responder).

<Radio Quality Information>

The radio quality information, herein is the information indicating theradio quality generated by the SR responder for each predetermined band,and indicates, for example, the following information.

-   (1) CCA result (Idle/Busy) indicating whether or not SR responder    can receive the SR signal (i.e., whether or not SR initiator can    transmit the SR signal).-   (2) Information indicating whether the interference level measured    by the SR responder is above or below a predetermined threshold.-   (3) Interference level measured by SR responder.-   (4) Received quality information (e.g., SINR) from SR initiator to    SR responder.

For example, in case of (2), when receiving radio quality informationindicating that the interference level is lower than a predeterminedthreshold, SR transmission resource controller 107 may determine thatthe SR signal can be received in the SR responder. Further, in case of(3), SR transmission resource controller 107 determines whether or notthe interference level is lower than a predetermined threshold, and whenthe interference level is lower than the threshold, SR transmissionresource controller 107 may determine that the SR signal can be receivedin the SR responder. In case of (4), SR transmission resource controller107 determines whether or not SINR is greater than a predeterminedthreshold, and when SINR is greater than the threshold, SR transmissionresource controller 107 may determine that the SR signal can be receivedin the SR responder.

The predetermined band where the radio quality information is definedmay be, for example, a band of the smallest allocation unit (in unis ofRUs (Resource Units) of OFDMA, as illustrated in FIG. 9. FIG. 9indicates, as an example, radio quality information (SR availabilityinformation) for each RU indicating whether or not the SR initiator inthe case of (1) can transmit the SR signal (sendable/unsendable).

In FIG. 9, SR transmission resource controller 107 allocates a frequencyresource for the SR signal to the RU (RU with low interference level)with which SR transmission is allowed. Meanwhile, SR transmissionresource controller 107 does not allocate a frequency resource for theSR signal to the RU with which SR transmission is not allowed (RU withhigher interference level).

The Non-SR signal from an OBSS STA indicated by a trigger frame, herein,is an UL OFDMA signal, and is the signal resulting from multiplexing ofsignals from a plurality of STAs by frequency multiplexing in units ofRUs. For this reason, in Non-SR signals, it is assumed that theinterference level fluctuates greatly in units of RUs depending on OFDMAallocation by a plurality of STAs.

Therefore, defining the radio quality information in units of RUs allowsSR transmission resource controller 107 to allocate a frequency resourcefor SR signals taking into consideration the increase or decrease of theinterference level depending on OFDMA allocation of the STA thattransmits a Non-SR signal. Thus, it is made possible to prevent adecrease in the reception success rate of the SR signal in the SRresponder and thus to improve the system performance.

Alternatively, the predetermined band defining the radio qualityinformation may be, for example, a band in units of 20 MHz bands asillustrated in FIG. 10. FIG. 10 illustrates, as an example, the radioquality information (SR availability information) for each channel in 20MHz band indicating whether or not the SR initiator in the case of (1)can transmit an SR signal (sendable or unsendable).

In case of FIG. 10, SR transmission resource controller 107 allocatesthe frequency resource for the SR signal to the band where SRtransmission is allowed (20 MHz channel with a low interference level).Meanwhile, SR transmission resource controller 107 does not allocate afrequency resource for the SR signal to the band where SR transmissionis not allowed (20 MHz channel with a high interference level).

The average interference level of interference given to the SR responderdepends on arrangement of APs around the SP responder. In addition, theprimary channel configured by each AP is in units of 20 MHz, so that asto the interference given to the SR responder, it is assumed that theinterference level greatly fluctuates in units of 20 MHz, depending onthe arrangement of surrounding APs.

Therefore, defining the radio quality information in units of 20 MHzallows SR transmission resource controller 107 to allocate the frequencyresource for the SR signal taking into consideration the increase ordecrease of the interference level depending on the surrounding APenvironment of the SR responder. Thus, it is made possible to prevent adecrease in the reception success rate of SR signals in SR respondersand thus to improve the system performance.

[Generation Method for Band Allocation Information for SR Signals]

Next, a detailed description will be given of the generation method forbandwidth allocation information (RU allocation information) for SRtransmission signals in preamble generator 109 of radio communicationapparatus 100 (SR initiator).

Preamble generator 109 determines the band allocation information (RUallocation information) based on the transmission band informationinputted from SR transmission resource controller 107, taking intoaccount the signaling bit amount and the degree of freedom ofallocation.

For example, preamble generator 109 may generate the band allocationinformation by performing bitmap arrangement for a flag indicating thepresence or absence of an allocation band for an SR signal for eachpredetermined band (e.g., in units of RUs or in units of 20 MHz). Thisallows the frequency resource for the SR signal to be allocated for eachpredetermined band without constraints (i.e., freely). Meanwhile, thesignaling bit amount increases in bitmap arrangement for eachpredetermined band.

Alternatively, preamble generator 109 may generate the band allocationinformation by performing bitmap arrangement for a flag indicating thepresence or absence of the allocation band for the SR signal for each RUgroup (RUG) composed of a plurality of consecutive RUs. As a result, thesignaling bit mount can be reduced as compared with bitmap allocation inunits of RUs. Meanwhile, there occurs a constraint in which thefrequency resource allocation for an SR signal is in units of RUGs, andas a result, the scheduling gain is reduced compared with allocation inunits of RUs.

Preamble generator 109 may generate the band allocation information byreusing RU Allocation subfield included in User Info field of thetrigger frame. Accordingly, application of the allocation rules ofexisting systems makes implementation easier, and the signaling bitamount can be reduced as well. Meanwhile, there is a constraint on thefrequency-resource allocation for an SR signal, which reduces thescheduling gain.

Preamble generator 109 may determine a generation method by taking intoaccount an allowable amount of overhead (signaling bit amount) assumedin the radio communication system and an expected scheduling gain, andgenerate band allocation information. Accordingly, the systemperformance can be improved.

Note that, the above-described generation method for band allocationinformation for SR signals can be similarly applied to radio qualityinformation generator 205 of the SR responder. Specifically, radioquality information generator 205 may indicate radio qualityinformation, such as the magnitude of measured interference level, oravailability of transmission of an SR signal (availability ofreception), as 1-bit information for each predetermined band (e.g., RUor 20 MHz). In this case, as described above, radio quality informationgenerator 205 may determine the generation method for radio qualityinformation by taking into account the signaling bit amount and thedegree of freedom of indication of radio quality information.Accordingly, radio quality information generator 205 can generateappropriate radio quality information taking into account the allowableamount for overhead and the expected scheduling gain assumed in theradio communication system, thereby making it possible to improve thesystem performance.

The generation method for band allocation information has beendescribed, thus far.

[Effects]

As described above, according to the present embodiment, radiocommunication apparatus 100 (SR initiator) determines a transmissionresource (frequency resource) for an SR signal transmitted by SR for anOBSS other than the BSS to which radio communication apparatus 100belongs, based on radio quality information transmitted from radiocommunication apparatus 200 (SR responder), which is another radiocommunication apparatus in the BSS to which the apparatus belongs, andtransmits the SR signal, using the determined transmission resource.

Thus, the SR initiator can determine the transmission resource (band)for the SR signal in accordance with the radio channel condition (e.g.,interference state) in the SR responder and transmit the SR signal.Therefore, according to the present embodiment, the system performancecan be improved by reducing the interference given by Non-SRtransmission of an OBSS to the BSS (SR responder) performing SRtransmission, and thus improving the reception success rate of the SRsignal.

Further, in the present embodiment, the SR initiator transmits no SRsignal in the band where the reception success rate of SR signals in theSR responder is determined to be low. Accordingly, it is made possibleto prevent SR signals from becoming an interference source for an OBSSwhich is not subject to interference reduction and which is closer tothe SR initiator than an OBSS subject to interference reduction is inthe band where no SR signal is not transmitted.

Embodiment 2

In this embodiment, a description will be given of a method forcontrolling SR transmission by an SR initiator based on a BSS color.

In the following description, a group of BSSs having a particular BSScolor is called “SRG (Spatial Reuse Group).”

The BSSs that belong to different SRGs are managed by differentoperators. Therefore, in the present embodiment, when performing SRtransmission to an OBSS belonging to an SRG different from the BSS towhich the SR initiator belongs, the SR initiator controls SRtransmission such that no interference is given to a surrounding OBSSother than an OBSS for which SR transmission is to be performed.

The SR initiator and SR responder according to the present embodimenthave the same basic configuration as radio communication apparatus 100and radio communication apparatus 200 according to Embodiment 1, so thatthe SR initiator and SR responder will be described with reference toFIGS. 4 and 5.

[Configuration of SR Initiator]

Radio communication apparatus 100 (SR initiator) according to thepresent embodiment receives a radio frame including a trigger frametransmitted from an OBSS, then determines the availability of SRtransmission based on the acquired BSS color of the OBSS or an SRG, andthe radio quality information transmitted from the SR responder, andwhen SR transmission is available, radio communication apparatus 100transmits an SR signal within a predetermined period.

Radio communication apparatus 100 according to the present embodiment isdifferent from radio communication apparatus 100 according to Embodiment1 in operation of SR transmission resource controller 107.

Further, the radio quality information held by radio quality informationholder 106 is radio quality information for each SRG or for each BSScolor (BSS).

Specifically, SR transmission resource controller 107 acquires, fromcontrol information included in the preamble inputted from decoder 104,a BSS color corresponding to the OBSS (OBSS to which OBSS STA thattransmits a Non-SR signal belongs) that becomes an interference sourcefor the SR signal.

Further, SR transmission resource controller 107 determines whether ornot the OBSS (BSS color) which becomes an interference source for the SRsignal is the same SRG as the BSS to which the apparatus belongs, basedon the SRG information (e.g., SRG BSS Color Bitmap subfield) included ina beacon frame transmitted by an AP in the BSS to which the apparatus(radio communication apparatus 100) belongs. Note that, in the followingdescription, the BSS having a BSS color belonging to the same group asthe BSS color of the BSS (its BSS) to which the SR initiator and SRresponder belong is simply referred to as “SRG,” and the BSS having aBSS color belonging to another group is referred to as “Non-SRG.”

SR transmission resource controller 107 determines the availability ofSR transmission, based on radio quality information on each SRG or eachBSS color, which is inputted from radio quality information holder 106.For example, SR transmission resource controller 107 determines theavailability of SR transmission based on radio quality information onthe group (SRG or Non-SRG) to which the OBSS that becomes aninterference source to the SR signal belongs in the radio qualityinformation for each SRG. Alternatively, SR transmission resourcecontroller 107 determines the availability of SR transmission based onradio quality information on the BSS color corresponding to OBSS whichbecomes an interference source to the SR signal in the radio qualityinformation on each BSS color.

When determining that SR transmission is not available, SR transmissionresource controller 107 cancels SR transmission by turning OFF theoutput from SR transmission resource controller 107 or outputtinginformation indicating that no SR transmission has been performed.

Meanwhile, when determining that SR transmission is available, SRtransmission resource controller 107 determines the time resource andthe transmission power resource for the SR signal as in Embodiment 1.That is, SR transmission resource controller 107 configures thetransmission power inputted from SR transmission power reducer 105 asthe transmission power resource. In addition, SR transmission resourcecontroller 107 may configure a time shorter than the packet length oftrigger-based PPDU (Non-SR signal) as a time resource. In addition, SRtransmission resource controller 107 may configure a predetermined bandin accordance with the transmission data size of the SR signal includingthe primary channel, for example, as the frequency resource.

SR transmission resource controller 107 outputs the determined SRtransmission resource to encoder 108 and radio transceiver 101. Notethat, a detailed description of a determination method for SRtransmission resources according to a BSS or SRG in SR transmissionresource controller 107 will be given, hereinafter.

[Configuration of SR Responder]

Radio communication apparatus 200 (SR responder) according to thepresent embodiment transmits radio quality information indicating aninterference level, SINR, availability of SR transmission and/or thelike for each group (SRG or Non-SRG) on a predetermined BSS color oreach BSS color to radio communication apparatus 100, and also receivesan SR signal from radio communication apparatus 100.

Radio communication apparatus 200 according to the present embodiment isdifferent from radio communication apparatus 200 according to Embodiment1 in operations of radio quality measurer 204 and radio qualityinformation generator 205.

Specifically, radio quality measurer 204 measures radio quality in unitsof BSS colors or in units of SRGs. That is, radio quality measurer 204measures the received power or interference level of the received signalinputted from radio transceiver 201 for each BSS color or for each SRG,and outputs the measurement result to radio quality informationgenerator 205.

Radio quality information generator 205 generates radio qualityinformation for each BSS color or radio quality information for each SRGby using the measurement result of the radio quality, which is measuredin units of BSS colors or in units of SRGs.

[Determination Method for Availability of Transmission of SR Signals]

Next, a detailed description will be given of a determination method foravailability of transmission of SR signals in SR transmission resourcecontroller 107 of radio communication apparatus 100 (SR initiator).

SR transmission resource controller 107 determines the availability ofSR transmission based on the radio quality information received from theSR responder.

<Radio Quality Information>

The BSS which is a Non-SRG is managed by an operator different from anoperator managing the BSS which is an SRG (including its BSS). For thisreason, when the SR initiator applies SR transmission to the OBSS whichis a Non-SRG, it is assumed that the interference given to an OBSS otherthan the target OBSS is reduced.

Therefore, in the present embodiment, radio quality measurer 204 of theSR responder determines the BSS color of the received signal andmeasures the radio quality of each of the SRG and Non-SRG (e.g.,interference level).

Then, radio quality information generator 205 of the SR responderrespectively configures the SRG and Non-SRG with thresholds, anddetermines that SR transmission is available (that is, SR signal can bereceived) when the interference level of the received signal, which ismeasured by radio quality measurer 204, is equal to or less than thethreshold and determines that the SR transmission is not available whenthe interference level is equal to or greater than the threshold (thatis, SR signal cannot be received). That is, the radio qualityinformation indicates the radio quality for each of the SRG and Non-SRG.For example, FIG. 11 illustrates the radio quality information (SRavailability information) indicating the availability of an SR signalwith respect to the SRG and Non-SRG, which is generated by radio qualityinformation generator 205.

Thus, the availability of SR transmission can be determined by takinginto account the increase or decrease of the interference level for eachSRG and Non-SRG depending on an OBSS environment around the SRresponder, so that it is made possible to prevent a decrease in thereception success rate of SR signals in the SR responder and thus toimprove the system performance.

Note that, as described above, since a Non-SRG is managed by an operatordifferent from an operator managing the BSS to which the SR initiatorand SR responder belong, it is desirable that the interference given bySR-transmission for the Non-SRG be small. In this respect, for example,in order to reduce the interference given by SR transmission to theOBSS, which is a Non-SRG, when the radio quality information isgenerated in the SR responder, the threshold for the interference levelof a Non-SRG may be small as compared with the threshold for theinterference level of SRG. Accordingly, the possibility of SRtransmission being applied to the Non-SRG as compared with an SRG isreduced. In this manner, the possibility of receiving interference by SRtransmission can be reduced in Non-SRG.

Further, radio quality information generator 205 may prohibit all SRtransmissions to Non-SRG and configure an SRG with a threshold for theinterference level. For example, radio quality information generator 205need not generate radio quality information for Non-SRG, and may setradio quality information for Non-SRG to be always unsendable. When thereceived signal is an SRG, SR radio resource controller 107 of the SRinitiator may determine the availability of SR transmission based on theradio quality information. Accordingly, the SR initiator can determinethe SR availability by taking into account the increase or decrease inthe interference level of only SRG depending on the OBSS environmentaround SR responder, so that it is made possible to prevent a decreasein the reception success rate of SR signals in SR responders and thus toimprove the system performance.

Further, the interference given to the SR responder depends onarrangement of surrounding OBSSs. It is assumed that a largeinterference is given to the SR responder from a particular OBSSdepending on the arrangement of OBSSs. Thus, radio quality measurer 204of the SR responder may measure the interference level in unis of BSScolors (i.e., in units of BSSs). Then, radio quality informationgenerator 205 may configure all BSS colors with a threshold for aninterference level common to all the BSS colors, and as illustrated inFIG. 12, radio quality information generator 205 may determine, for eachBSS color, that SR transmission is available when the interference levelis less than the threshold, and determine, for each BSS color, that SRtransmission is not available when the interference level is equal to orgreater than the threshold. That is, the radio quality informationindicates the radio quality for each BSS. Thus, the SR availability canbe determined by taking into account the increase or decrease in theinterference level in units of individual OBSSs depending on an OBSSenvironment around the SR responder, so that it is made possible toprevent a decrease in the reception success rate of SR signals in SRresponders and thus to improve the system performance.

Note that, the radio quality information to be broadcasted by an SRresponder to SR initiators is not limited to the information indicatingthe availability of transmission of SR signals illustrated in FIGS. 11and 12. For example, radio quality information indicating theinterference level of each of SRG and Non-SRG may be broadcasted. Inthis case, SR transmission resource controller 107 of the SR initiatormay determine the availability of SR transmission based on theinterference level indicated in the radio quality information and theconfigured threshold.

In FIG. 11, the case has been described where the radio qualityinformation for two groups of SRG and Non-SRG is used, but the radioquality information for three or more groups (e.g., SRG and a pluralityof Non-SRGs) may be used.

[Determination Method for Transmission Resources for SR Signals]

Next, a detailed description will be given of a determination method fortransmission resources for SR signals in SR transmission resourcecontroller 107 of an SR initiator.

SR transmission resource controller 107 determines the availability ofSR transmission based on the radio quality information received from theSR responder, and the BSS color of the received signal (OBSS signal).That is, SR transmission resource controller 107 determines theavailability of SR transmission based on radio quality information ofthe group (SRG or Non-SRG) to which the BSS color included in thereceived signal belongs in the radio quality information (e.g., see FIG.11 or 12) for each SRG/Non-SRG or each BSS color.

SR transmission resource controller 107 determines the time resource andtransmission power resource for SR signals, as in Embodiment 1, when thedetermination result of SR transmission on the BSS color of the receivedsignal is sendable. That is, SR transmission resource controller 107configures the transmission power inputted from SR transmission powerreducer 105, as the transmission power resource. In addition, SRtransmission resource controller 107 may configure a time shorter thanthe packet length of a trigger-based PPDU (Non-SR signal) as the timeresources. In addition, SR transmission resource controller 107 mayconfigure a predetermined band in accordance with the transmission datasize of the SR signal including the primary channel as the frequencyresource.

Meanwhile, when the determination result of SR transmission with respectto a BSS color of the received signal indicates unsendable, SRtransmission resource controller 107 cancels the SR transmission byturning off the output from SR transmission resource controller 107 oroutputting information indicating that no SR transmission has beenperformed.

The determination method for transmission resources of SR signals hasbeen described, thus far.

[Effects]

As described above, in the present embodiment, the SR initiator (radiocommunication apparatus 100) controls SR transmission in units ofSRGs/Non-SRGs or in units of BSSs based on the radio quality informationfrom the SR responder (radio communication apparatus 200). Accordingly,the SR initiator is allowed to preferentially apply SR transmission toan OBSS that is an SR sendable group or BSS (e.g., the group or BSS thatgive a small interference to the SR responder. Therefore, according tothe present embodiment, the system performance can be improved byreducing the interference given by an OBSS to the SR responder, and thusimproving the reception success rate of SR signals in SR responders.

Further, in the present embodiment, the SR initiator does not apply SRtransmission to the SRG or the BSS for which the SR initiator hasdetermined that the reception success rate of SR signals in the SRresponder is low. Accordingly, it is possible to prevent SR signals frombecoming an interference source to an OBSS that is not subject tointerference reduction and that is closer to the SR initiator than anOBSS subject to interference reduction is.

As described above, it is assumed that a Non-SRG different from an SRGincluding a BSS to which the SR initiator and SR responder belong ismanaged by a different operator. In this respect, according to thepresent embodiment, the SR initiator cancels SR transmission in a casewhere the interference by Non-SR signal from an OBSS of Non-SRG is largeand a decoding error of the SR signal in the SR responder is likely tooccur, even when performing SR transmission for an OBSS belonging to anSRG different from the BSS to which the apparatus belongs. Thus, thereis no interference due to SR transmission in Non-SRGs. That is, the SRinitiator can control SR transmission so as not to give interference toa surrounding OBSS other than the OBSS which is an SR transmissiontarget in Non-SRGs.

Embodiment 3

Regarding the transmission power for SR signals, the maximum power isderived by Equation 2 in order to reduce the interference to an OBSS,but the minimum power is not determined. Therefore, depending on thevalues of SRP and RSSI acquired from a trigger frame transmitted by theOBSS, the transmission power for the SR signal becomes small, and thereception success rate in the SR responder is reduced in some cases.

In this respect, in the present embodiment, a description will be givenof a method for improving the reception success rate of SR signals in SRresponders by guaranteeing the received qualities of the SR signals inthe SR responders.

[Configuration of SR Initiator]

FIG. 13 is a block diagram illustrating a configuration example of radiocommunication apparatus 300 according to the present embodiment. Radiocommunication apparatus 300 (SR initiator) according to the presentembodiment determines the availability of SR transmission based oninformation that can be acquired from a trigger frame of an OBSS (suchas SRP and RSSI) and radio quality information from the SR responder,and when SR transmission is available, radio communication apparatus 300(SR initiator) transmits an SR signal within a predetermined period.

In FIG. 13, the same components as those of Embodiment 1 (FIG. 4) aredenoted by the same reference numerals, and their descriptions will notbe repeated. Specifically, radio communication apparatus 300 isdifferent from radio communication apparatus 100 according to Embodiment1 in that radio communication apparatus 300 is not provided with SRtransmission power reducer 105, and is different in operation of SRtransmission resource controller 301.

The radio quality information to be held by radio quality informationholder 106 is information indicating SINR in the SR responder whencommunication is performed from the SR initiator (radio communicationapparatus 300) to the SR responder (radio communication apparatus 200).

Specifically, SR transmission resource controller 301 calculatestransmission power for the SR signal (corresponding to allowable powerto be described, hereinafter, i.e., transmission power calculated fromSRP), using an SRP [dBm] included in a trigger frame inputted fromdecoder 104 and an RSSI (RSSI_(trigger frame)) of a trigger frameinputted from received power measurer 102.

SR transmission resource controller 301 calculates a guaranteed powerthat satisfies a predetermined packet error rate (PER) in the SRresponder, based on radio quality information (SINR information)acquired from radio quality information holder 106.

When the transmission power calculated from the SRP does not satisfy theguaranteed power (when the transmission power is less than theguaranteed power), SR transmission resource controller 301 determinesthat SR transmission is not available, and cancels the SR transmission.

Meanwhile, when the transmission power calculated from the SRP satisfiesthe guaranteed power (when the transmission power calculated from theSRP is greater than the guaranteed power), SR transmission resourcecontroller 301 determines that SR transmission is available, anddetermines the transmission resource for the SR signal. Specifically, SRtransmission resource controller 301 determines the time resource andthe frequency resource as in Embodiment 1 or 2. That is, SR transmissionresource controller 301 configures a time shorter than the packet lengthof Trigger-based PPDU (Non-SR signal) as the time resource, andconfigures a predetermined band in accordance with the transmission datasize of the SR transmission signal including a primary channel, as thefrequency resource.

Further, SR transmission resource controller 301 determines thetransmission power resources based on the transmission power calculatedfrom the SRP and the guaranteed power. Note that, a detailed descriptionof a determination method for SR transmission resources (transmissionpower resources) in SR transmission resource controller 301 will begiven, hereinafter.

[Configuration of SR Responder]

The SR responder according to the present embodiment has the same basicconfiguration as radio communication apparatus 200 according toEmbodiment 1, the SP responder will be described with reference to FIG.5.

Radio communication apparatus 200 (SR responder) according to thepresent embodiment transmits, using a received signal from an SRinitiator, the radio quality information indicating an SINR and/or thelike to radio communication apparatus 100 and receives an SR signal fromradio communication apparatus 100.

Radio communication apparatus 200 according to the present embodiment isdifferent from radio communication apparatus 200 according to Embodiment1 in operations of radio quality measurer 204 and radio qualityinformation generator 205.

Specifically, radio quality measurer 204 measures the received quality(e.g., SINR) from the received signal of the SR initiator, which isinputted from the radio transceiver 201, and outputs the measurementresult to radio quality information generator 205.

Radio quality information generator 205 generates a management frame ora control frame addressed to the SR initiator including the measurementresult including the SINR inputted from radio quality measurer 204, andoutputs the management frame or control frame to modulator 206.

[Determination Method for Transmission Power for SR TransmissionSignals]

Next, a more detailed description will be given of the determinationmethod for transmission power resources in SR transmission resourcecontroller 301.

In a case where the SR initiator performs SR transmission to an OBSS, itis assumed that the reception success rate is reduced because thereceived SINR of the SR signal in the SP responder does not satisfy therequired quality due to the influence of the interference to the SPresponder based on the arrangement of surrounding OBSSs depending on thetransmission power for the SR signal required by the reduction processof the interference given to the OBSS (i.e., the transmission powercalculated from the SRP).

In this respect, SR transmission resource controller 301 of the SRinitiator determines the transmission power for the SR signal based onthe received quality indicated in the radio quality information receivedfrom the SR responder. The received quality illustrated in the radioquality information, herein, is, for example, an SINR when the SRinitiator performs transmission to the SR responder with a predeterminedpower. Specifically, SR transmission resource controller 301 calculatesthe transmission power (guaranteed power) required for a PER of apredetermined MCS (e.g., the most robust MCS) to satisfy the targetusing SINR information included in the radio quality information.

Then, SR transmission resource controller 301 determines thetransmission power (TXPWR_(SR initiator)) for the SR signal, using thecalculated guaranteed power, the SRP [dBm] included in a trigger frame,and RSSI (RSSI_(trigger frame)) of a trigger frame inputted fromreceived power measurer 102 as follows.

SR transmission resource controller 301 needs to keep the transmissionpower for the SR signal less than the power (referred to as allowablepower (TXPWR_(Allowed))) calculated according to the following Equation3 in order to keep the interference given to the OBSS to be less than anallowable value.

TXPWR_(Allowed)=SRP−RSSI_(trigger frame)   (3)

Specifically, when the allowable power is greater than guaranteed power(Guaranteed power<TXPWR_(Allowed)), SR transmission resource controller301 configures the transmission power (TXPWR_(SR initiator)) for the SRsignal in the range (range in which the value is greater than theguaranteed power and less than the allowable power) illustrated inEquation 4.1. In this case, the SR initiator can use the transmissionpower that minimizes the interference given to the OBSS that is the SRtransmission target, while guaranteeing the received quality in the SRresponder. Accordingly, it is made possible to reduce the interferencegiven to the OBSS which is not the SR transmission target, so that it ispossible to increase the number of transmission opportunities for OBSSsand thus to improve the system performance.

$\mspace{79mu} {\lbrack 1\rbrack {{TXPWR}_{{SR}\mspace{14mu} {initiator}} = \left\{ \begin{matrix}{{{Guranteed}\mspace{14mu} {power}} < {TXPWR}_{{SR}\mspace{14mu} {initiator}} <} & (4.1) \\{{TXPRW}_{Allowed}\left( {{{Guranteed}\mspace{14mu} {power}} < {TXPRW}_{Allowed}} \right)} & \; \\{{Prohibit}\left( {{{Guranteed}\mspace{14mu} {power}} \geq {TXPRW}_{Allowed}} \right)} & (4.2)\end{matrix} \right.}}$

Further, when the allowable power is equal to or less than theguaranteed power (Guaranteed power≥TXPWR_(Allowed)), SR transmissionresource controller 301 cancels (prohibits) SR transmission because thetransmission power for the SR signal does not satisfy the guaranteedpower. As a result, the SR initiator can avoid SR-transmission with alow reception success rate in the SR responder. For this reason, it ismade possible to prevent a decrease in the reception success rate of SRsignals and thus to improve the system performance.

[Effects]

As described above, in the present embodiment, the SR initiator performsSR transmission with the transmission power that guarantees the receivedquality of the SR signal in the SR responder. That is, the SR initiatorperforms no SR transmission in a case where the received quality of theSR signal cannot be guaranteed in the SR responder. As described above,the SR initiator can determine the transmission resource (transmissionpower) for the SR signal in accordance with the radio channel condition(e.g., SINR) in the SR responder and transmit the SR signal. Therefore,according to the present embodiment, the reception success rate of SRsignals is improved by reducing the interference given by the OBSS tothe SR responder and also guaranteeing the received quality of the SRsignal in the SR responder, and thus, the system performance can beimproved.

Further, in the present embodiment, the SR initiator transmits no SRsignals in the band where the reception success rate of SR signals inthe SR responder is determined to be low. Accordingly, it is madepossible to prevent the SR signal from becoming an interference sourceto an OBSS that subject to interference reduction and that is closer tothe SR initiator than an OBSS subject to interference reduction targetis.

Each embodiment of the present disclosure has been described, thus far.

Other Embodiments

-   (1) At least two of Embodiments 1, 2, and 3 may be applied in    combination. For example, an SR initiator may determine the    availability of transmission of an SR signal in units of SRGs as    described in Embodiment 2, and further, in the SRG with which the SR    signal is sendable, the SR initiator may determine the availability    of transmission of an SR signal in units of predetermined bands as    described in Embodiment 1. Further, for example, the SR initiator    may determine the availability of transmission of an SR signal as    described in Embodiment(s) 1 and/or 2, and transmit the SR signal to    satisfy the guaranteed power, as described in Embodiment 3.

(2) In radio communication apparatus 100 (see FIG. 4) according toEmbodiments 1 and 2, the processing order of the processing of SRtransmission resource controller 107 (i.e., determination oftransmission resources) and the processing of SR transmission powerreducer 105 (i.e., reduction of transmission power based on SRPs) may beswitched. For example, when SR transmission resource controller 107determines that SR transmission is not available (cancels SRtransmission) based on the radio quality information, SR transmissionpower reducer 105 does not perform the processing. As a result, theprocessing amount in radio communication apparatus 100 can be reduced.

(3) When receiving a BSS signal or OBSS signal, the SR responder mayupdate the radio quality information and broadcast the radio qualityinformation addressed to the STAs in the BSS to which SR responderbelongs.

(4) In the above embodiment, the case has been described where the SRinitiator is an STA, and the SR responder is an AP, but the presentinvention is not limited to this case. For example, the embodimentdescribed above can be applied even when the SR initiator is an AP andthe SR responder is an STA, and the same effects can be obtained.

Note that, the operation when the SR initiator is an AP and the SRresponder is an STA is the same as the operation example illustrated inFIG. 6. That is, as in FIG. 6, the SR responder (STA) transmits theradio quality information to the SR initiator (AP) in a predeterminedcycle or at a predetermined timing. The SR initiator (AP) determines theavailability of SR transmission based on the radio quality informationfrom the SR responder (STA), and when SR transmission is available, theSR initiator (AP) performs SR transmission, using the availabletransmission resource.

Note that, the SR initiator (AP) may transmit a signal (radio qualityinformation request signal) requesting radio quality information to theSTAs in the BSS to which the SR initiator belongs (not illustrated). TheSTA that has received the radio quality information request signaltransmits a response signal including the radio quality information tothe SR initiator. For example, the SR initiator (AP) may use a triggerframe (trigger frame whose trigger type is bandwidth query report poll(BQRP)) requesting the STA for transmission of bandwidth query report(BQR), as the radio quality information request signal, and transmit thetrigger frame to STAs in the BSS to which the SR initiator belongs. Inthis case, the STA transmits the BQR as the radio quality information,as a response signal to the radio quality information requesting signal.As described above, the process requesting the radio quality informationcan be easily issued by using radio quality information acquisitionmeans already defined in 11ax.

In addition, the above embodiment can be applied even when both of theSR initiator and SR responder are STAs, and the same effects can beobtained.

(5) In the above embodiment, SRP-based SR (DSRP_PPDU-based SR) using atrigger frame of an OBSS has been described as an example, but the aboveembodiment can be applied to another SRP-based SR, and the same effectcan be obtained.

When the above-described embodiment is applied to the other SRP-basedSR, the method for acquiring an SRP and the method for measuring an RSSIare different as compared with DSRP_PPDU-based SR. Incidentally, theother SRP-based SR includes, for example, TSRP (Trigger-basedSRP)_PPDU-based SR, using PPDU other than a trigger frame of an OBSS,ULSRP (Uplink SRP)_PPDU-based SR using a beacon and a response frame ofan OBSS, or DLSRP (Downlink SRP)_PPDU-based SR using CTS (Clear to Send)of an OBSS (e.g., see NPL 1). Hereinafter, these SRP-based SR methodsare referred to as “SRP-based SR using a preceding signal.”

FIG. 14 is a sequence diagram illustrating an operation example ofSRP-based SR using a preceding signal. Note that, in FIG. 14, the sameoperations as those in FIG. 6 are denoted by the same referencenumerals, and their descriptions will not be repeated.

In FIG. 14, the OBSS AP transmits a preceding signal to the OBSS STA(ST301). The preceding signal is a signal having the same BSS color asthe signal transmitted by the OBSS STA. Specifically, the precedingsignal is a PPDU, a beacon frame, a CTS frame, a BlockACK (BA) frame, oran Acknowledgement (ACK) frame that cannot be identified from a triggerframe.

In ST301, the SR initiator receives the preceding signal transmitted bythe OBSS AP, measures an RSSI for each frame type of the receivedpreceding signal and saves the RSSI.

The SR initiator then receives a Non-SR signal transmitted by the OBSSSTA and addressed to the OBSS AP and acquires the packet lengths of theSRP and Non-SR signal based on the Non-SR signal (ST302). In addition,the SR initiator identifies the PPDU format in the Non-SR signal andacquires an RSSI of a signal satisfying a predetermined condition (e.g.,the frame type corresponding to the PPDU format) from among the RSSIs ofthe saved preceding signals. The SR initiator then determines thetransmission power for the SR signal to reduce interference to the OBSSAP (e.g., see Equation 2), using the acquired SRP and RSSI (ST303). Inaddition, the SR initiator determines an SR transmission period (SRPopportunity) based on the acquired packet length of the Non-SR signal(ST304).

That is, in FIG. 14, the SR initiator is different from FIG. 6 in thatthe SR initiator acquires the packet lengths of the SRP and Non-SRsignal from the Non-SR signal transmitted from the OBSS, and that the SRinitiator acquires the RSSI measured from the preceding signal inaccordance with the format of the Non-SR signal.

FIG. 15 is a block diagram illustrating a configuration example of radiocommunication apparatus 400, which is an SR initiator for performingSRP-based SR using a preceding signal. Note that, in FIG. 15, the samecomponents as those of Embodiment 1 (FIG. 4) are denoted by the samereference numerals, and their descriptions will not be repeated.Specifically, radio communication apparatus 400 is different from FIG. 4in that radio communication apparatus 400 includes received power holder401.

Received power holder 401 acquires an RSSI measured using a precedingsignal of an OBSS from received power measurer 102 and saves the RSSIfor a predetermined period of time. Further, received power holder 401acquires a BSS color, a data format, and SRP information that can beacquired from a Non-SR signal of the OBSS from decoder 104, and savesthe acquired information for a predetermined period of time.

Then, when a PPDU having a predetermined SRP is inputted, received powerholder 401 outputs an RSSI of a preceding signal satisfying apredetermined condition corresponding to the format of the inputted PPDUto SR transmission power reducer 105. Meanwhile, received power holder401 saves the information contained in the inputted signal, when asignal with no predetermined SRP is inputted or when an RSSI of apreceding signal that satisfies the predetermined condition is not held.In this case, the SR initiator (e.g., SR controller) cancels SRtransmission.

(6) Although the above embodiment has been described with the assumptionof SRP-based SR, the above embodiment can be applied to the cases ofOBSS PD-based SR, and the same effects can be obtained.

FIG. 16 is a sequence diagram illustrating an operation example of OBSSPD-based SR. In FIG. 16, the same operations as those in FIG. 6 aredenoted by the same reference numerals, and their descriptions will notbe repeated.

In FIG. 16, the OBSS STA transmits a non-SR signal to the OBSS AP(ST401). At this time, the SR initiator has received the Non-SR signaltransmitted from the OBSS STA to the OBSS AP.

The SR initiator determines whether the OBSS is an SRG or Non-SRG basedon the BSS color of the Non-SR signal transmitted by the OBSS STA, andwhen the received power for the Non-SR signal is a received power lessthan or equal to the OBSS_PD_(Threshold) determined based on Equation 5below, the SR initiator determines the transmission power for the SRsignal (ST402). At this time, the SR initiator does not take theinterference allowable value of the OBSS AP into consideration.

$\begin{matrix}{\mspace{79mu} \lbrack 2\rbrack} & \; \\{{OBSS\_ PD}_{Threshold} = {\max \begin{bmatrix}{OBSS\_ PD}_{{Threshold}\; \_ \; m\; i\; n} \\{\min \begin{pmatrix}{OBSS\_ PD}_{{Threshold}\; \_ \; {ma}\; x} \\{{OBSS\_ PD}_{{Threshold}\; \_ \; m\; i\; n} + \left( {{TXPWR}_{ref} - {TXPWR}} \right)}\end{pmatrix}}\end{bmatrix}}} & (5)\end{matrix}$

In Equation 5, OBSS_PD_(Threshold_min) is the minimum value taken byOBSS_PD_(Threshold), and OBSS_PD_(Threshold_max) is the maximum valuetaken by OBSS_PD_(Threshold). TXPWR_(ref) is a reference transmissionpower and TXPWR is the SR transmission power.

Next, the SR initiator then determines the transmission resource for theSR signal with which the desired received quality can be expected, basedon the radio quality information on a predetermined transmissionresource received from the SR responder (ST403). The SR transmissionpower is expressed by the following Equations 6.1 and 6.2 based on theoperation and Equation 5 described in Embodiment 3.

     [3] ${TXPWR}_{{ma}\; x} = \left\{ \begin{matrix}{{{Guranteed}\mspace{14mu} {power}} < {TXPWR}_{{ma}\; x}} & \left( {{OBSS\_ PD}_{level} \leq {OBSS\_ PD}_{\min}} \right) & (6.1) \\\begin{matrix}{{{Guranteed}\mspace{14mu} {power}} < {TXPWR}_{{ma}\; x} <} \\{{TXPWR}_{ref} -} \\\left( {{OBSS\_ PD}_{level} - {OBSS\_ PD}_{\min}} \right)\end{matrix} & \begin{pmatrix}{{OBSS\_ PD}_{\max} \geq} \\{{OBSS\_ PD}_{level} >} \\{OBSS\_ PD}_{\min}\end{pmatrix} & (6.2)\end{matrix} \right.$

In case of Equation (6.1), when the received level (OBSS_PD_(level))from the OBSS is less than or equal to the minimum value (OBSS_PD_(min))of the OBSS level, it is sufficient that the maximum SR transmissionpower (TXPWR_(max)) satisfies a value greater than the guaranteed power.Meanwhile, in case of Equation 6.2, the SR transmission power is definedwithin a range of a value greater than the guaranteed power to a valueless than the reference transmission power, when the received level fromthe OBSS takes a value within the range between the maximum value(OBSS_PD_(max)) and the minimum value of the OBSS PD threshold. WhenEquations 6.1 and 6.2 are not satisfied, the SR initiator cancelsSR-transmission.

That is, in OBSS PD-based SR, the SR initiator is different from theSRP-based SR described in the embodiment described above with respect tothe following two points: the SR initiator does not perform interferencereduction processing for a particular OBSS based on the informationobtained from the signal of an OBSS AP as in the above embodiment; andthe operation in the power control method of Embodiment 3 (Equations 6.1and 6.2) is different.

(7) In the above embodiment, the case has been described in which anRSSI is used as an example of received power, but the parameterrepresenting received power is not limited to the RSSI. In addition,although the description has been given of the case where an SINR isused as an example of the received quality when communication isperformed from the SR initiator to the SR responder, the parameterrepresenting the received quality is not limited to the SINR.

(8) The present disclosure can be realized by software, hardware, orsoftware in cooperation with hardware. Each functional block used in thedescription of each embodiment described above can be partly or entirelyrealized by an LSI such as an integrated circuit, and each processdescribed in each embodiment may be controlled partly or entirely by thesame LSI or a combination of LSIs. The LSI may be individually formed aschips, or one chip may be formed so as to include a part or all of thefunctional blocks. The LSI may include a data input and output coupledthereto. The LSI herein may be referred to as an IC, a system LSI, asuper LSI, or an ultra LSI depending on a difference in the degree ofintegration. However, the technique of implementing an integratedcircuit is not limited to the LSI and may be realized by using adedicated circuit, a general-purpose processor, or a special-purposeprocessor. In addition, a Field Programmable Gate Array (FPGA) that canbe programmed after the manufacture of the LSI or a reconfigurableprocessor in which the connections and the settings of circuit cellsdisposed inside the LSI can be reconfigured may be used. The presentdisclosure can be realized as digital processing or analogue processing.If future integrated circuit technology replaces LSIs as a result of theadvancement of semiconductor technology or other derivative technology,the functional blocks could be integrated using the future integratedcircuit technology. Biotechnology can also be applied.

The present disclosure can be implemented in apparatuses, devices, andsystems of any kind, each being provided with a communication function,(collectively referred to as “communication apparatuses”). Non-limitingexamples of the communication apparatuses include telephones (such asportable phones and smartphones), tablets, personal computers (PCs)(such as laptops, desktops, and notebooks), cameras (such as digitalstill/video cameras), digital players (such as digital audio/videoplayers), wearable devices (such as wearable cameras, smartwatches, andtracking devices), game consoles, digital book readers, telehealthtelemedicine (remote healthcare medicine prescription) devices,communication-function-equipped vehicles or transportation (such asautomobiles, airplanes and ships), and a combination of the abovementioned apparatuses of various kinds.

The communication apparatuses are not limited to portable or mobileapparatuses and thus include unportable or fixed apparatuses, devices,and systems of any kind, such as smart home devices (e.g., appliances,lighting equipment, smart meters or measuring instruments, and controlpanels), vending machines, and Internet of Things (“IoT” (every “things”that may exist on networks.

In addition to data communication via cellular systems, wireless LANsystems, communication satellite systems and/or the like, communicationincludes data communication via a combination of these systems.

Moreover, the communication apparatuses include devices, such ascontrollers or sensors to be connected to or linked to a communicationdevice which executes communication functions described in the presentdisclosure. Controllers or sensors are included, for example, each ofwhich is configured to generate a control signal and/or a data signalused by the communication device which executes the communicationfunctions of the communication apparatuses.

Further, the communication apparatuses include infrastructure equipmentwhich performs communication with the above-mentioned non-limitingapparatuses of various kinds or which controls these non-limitingapparatuses of various kinds, such as base stations, access points,apparatuses of any other kinds, devices, and systems.

A radio communication apparatus according to the present disclosureincludes: control circuitry, which, in operation, determines atransmission resource for a Spatial Reuse (SR) signal based on radioquality information transmitted from another radio communicationapparatus in a first Basic Service Set (BSS), the SR signal beingtransmitted by SR for a second BSS which is a BSS other than the firstBSS; and transmission circuitry, which, in operation, transmits the SRsignal, using the transmission resource.

In the radio communication apparatus according to the presentdisclosure, the control circuitry determines, based on the radio qualityinformation, a band where the SR signal is sendable, and thetransmission circuitry transmits the SR signal in the band where the SRsignal is sendable, and the transmission circuitry does not transmit theSR signal in a band other than the band where the SR signal is sendable.

In the radio communication apparatus according to the presentdisclosure, the control circuitry determines the transmission resourcewhen transmitting the SR signal in a period obtained based on a signalfrom the second BSS, and the control circuitry does not determine thetransmission resource when not transmitting the SR signal in the period.

In the radio communication apparatus according to the presentdisclosure, the radio quality information indicates radio quality foreach predetermined band.

In the radio communication apparatus according to the presentdisclosure, the predetermined band is a band in units of resource units(RUs).

In the radio communication apparatus according to the presentdisclosure, the predetermined band is a band in units of 20 MHz.

In the radio communication apparatus according to the presentdisclosure, the radio quality information indicates any of: whether ornot the SR signal is receivable in the other radio communicationapparatus; whether or not an interference level in the other radiocommunication apparatus is lower than a threshold; the interferencelevel in the other radio communication apparatus; and received qualitywhen communication is performed from the radio communication apparatusto the other radio communication apparatus.

In the radio communication apparatus according to the presentdisclosure, the radio quality information indicates radio quality ofeach of the BSSs.

In the radio communication apparatus according to the presentdisclosure, the radio quality information indicates radio quality for aBSS that belongs to a first group including the first BSS, and radioquality for a BSS that belongs to a second group which is different fromthe first group.

In the radio communication apparatus according to the presentdisclosure, the radio quality information includes received quality whencommunication from the radio communication apparatus to the other radiocommunication apparatus is performed, and the control circuitrycalculates, based on the received quality, a first transmission powersatisfying a predetermined error rate in the other radio communicationapparatus, calculates a second transmission power based on a signal fromthe second BSS, and when the second transmission power is greater thanthe first transmission power, the control circuitry determinestransmission of the SR signal.

In the radio communication apparatus according to the presentdisclosure, the transmission power for the SR signal is greater than thefirst transmission power and is less than the second transmission power.

A radio communication method according to the present disclosureincludes: determining a transmission resource for a Spatial Reuse (SR)signal based on radio quality information transmitted from another radiocommunication apparatus in a first Basic Service Set (BSS), the SRsignal being transmitted by SR for a second BSS other than the firstBSS; and transmitting the SR signal, using the transmission resource.

The disclosure of Japanese Patent Application No. 2018-035456, filed onFeb. 28, 2018, including the specification, drawings, and abstract isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

One exemplary embodiment of the present disclosure is useful in radiocommunication systems.

REFERENCE SIGNS LIST

-   100, 200, 300, 400 Radio communication apparatus-   101, 201 Radio transceiver-   102 Received power measurer-   103, 202 Demodulator-   104, 203 Decoder-   105 SR transmission power reducer-   106 Radio quality information holder-   107, 301 SR transmission resource controller-   108 Encoder-   109 Preamble generator-   110, 206 Modulator-   204 Radio quality measurer-   205 Radio quality information generator-   401 Received power holder

1. A radio communication apparatus, comprising: control circuitry,which, in operation, determines a transmission resource for a SpatialReuse (SR) signal based on radio quality information transmitted fromanother radio communication apparatus in a first Basic Service Set(BSS), the SR signal being transmitted by SR for a second BSS which is aBSS other than the first BSS; and transmission circuitry, which, inoperation, transmits the SR signal, using the transmission resource. 2.The radio communication apparatus according to claim 1, wherein thecontrol circuitry determines, based on the radio quality information, aband where the SR signal is sendable, and the transmission circuitrytransmits the SR signal in the band where the SR signal is sendable, andthe transmission circuitry does not transmit the SR signal in a bandother than the band where the SR signal is sendable.
 3. The radiocommunication apparatus according to claim 1, wherein the controlcircuitry determines the transmission resource when transmitting the SRsignal in a period obtained based on a signal from the second BSS, andthe control circuitry does not determine the transmission resource whennot transmitting the SR signal in the period.
 4. The radio communicationapparatus according to claim 1, wherein the radio quality informationindicates radio quality for each predetermined band.
 5. The radiocommunication apparatus according to claim 4, wherein the predeterminedband is a band in units of resource units (RUs).
 6. The radiocommunication apparatus according to claim 4, wherein the predeterminedband is a band in units of 20 MHz.
 7. The radio communication apparatusaccording to claim 1, wherein the radio quality information indicatesany of: whether or not the SR signal is receivable in the other radiocommunication apparatus; whether or not an interference level in theother radio communication apparatus is lower than a threshold; theinterference level in the other radio communication apparatus; andreceived quality when communication is performed from the radiocommunication apparatus to the other radio communication apparatus. 8.The radio communication apparatus according to claim 1, wherein theradio quality information indicates radio quality of each of the BSSs.9. The radio communication apparatus according to claim 1, wherein theradio quality information indicates radio quality for a BSS that belongsto a first group including the first BSS, and radio quality for a BSSthat belongs to a second group which is different from the first group.10. The radio communication apparatus according to claim 1, wherein theradio quality information includes received quality when communicationfrom the radio communication apparatus to the other radio communicationapparatus is performed, and the control circuitry calculates, based onthe received quality, a first transmission power satisfying apredetermined error rate in the other radio communication apparatus,calculates a second transmission power based on a signal from the secondBSS, and when the second transmission power is greater than the firsttransmission power, the control circuitry determines transmission of theSR signal.
 11. The radio communication apparatus according to claim 10,wherein the transmission power for the SR signal is greater than thefirst transmission power and is less than the second transmission power.12. A radio communication method, comprising: determining a transmissionresource for a Spatial Reuse (SR) signal based on radio qualityinformation transmitted from another radio communication apparatus in afirst Basic Service Set (BSS), the SR signal being transmitted by SR fora second BSS other than the first BSS; and transmitting the SR signal,using the transmission resource.